A method of the above kind is disclosed, for example, in U.S. Pat. No. 6,226,576. In this patent, a method for monitoring and fault detection is described. Here, one distinguishes between such diagnostic functions which run through during the normal operation of the engine and monitor the function of a component and such diagnostic functions which actively influence a component and so determine the operability thereof.
Because of the statutory requirements of the California Air Resource Board (CARB), the running behavior or the running capability of diagnostic functions must be documented in everyday use in all future motor vehicles. In this way, the protection against failure, especially of environmentally critical components, is to be once again improved. For the fault diagnosis of specific components, a specific frequency of a fault identifying capability must be shown. The frequency of a fault identifying capability of a fault diagnosis is documented by a quotient in whose numerator a number of detected possibilities of a fault detection is present and, in whose denominator the number of time intervals is present in which specified driving conditions were present which are required for the diagnosis of specific components. This quotient is characterized as an in-use-monitor-performance-ratio.